Which of the following is not an antidote mentioned for drug overdoses?

Dextrose is primarily used to treat hypoglycemia, which is a condition characterized by low blood glucose levels, rather than acting as an antidote for drug overdoses. While it can be crucial in managing cases of insulin overdose or certain depressant overdoses where hypoglycemia is a factor, it does not directly counteract the toxic effects of most drugs.

On the other hand, glucagon acts as an antidote in cases of beta-blocker overdose by increasing heart rate and contractility, making it suitable for specific toxicities. Atropine is utilized as an antidote for organophosphate poisoning because it counters excessive acetylcholine at muscarinic receptors, reversing symptoms like bronchoconstriction and bradycardia. Flumazenil is an antagonist for benzodiazepines, helping to reverse their sedative effects in overdose situations. Each of these substances is specifically designed to counteract certain drug overdoses, highlighting their role as antidotes in toxicological emergencies.